How to remove Malware

I’m a beginner and I love it, but I’m getting frusterated with not being able to clean the machine of some malware. My machine is fine, but I keep running into family, which I’m working on now, that download the malware “your computer is infected” Windows has detected spyware infection! click this message to install the last update of windows security software… and then I think the “Warning! your’re in Danger” Wallpaper get’s going. I’ve googled it, and found some folders in Documents and Settings, found some registry keys that I’ve deleted, but it’s still there. What am I missing? Any help would be greatly appeciated.